Hi,

It's kind of chain reaction polymerization which perhaps failed in initiation. In this this polymerization reaction TEMED and APS are the initiators and some environmental factor may helps the initiation like as light, temperature and oxygen content (reversely effects) of solutions. Using old acrylamide and bis might be helpful as in old solutions some degree of polymerization took place and this helps you to make firm gel with low initiator concentration, therefore changing to new solution was not a good idea as always. 

Hope it works this time. if not increase APS concentration to reach the optiamal concentration. 

Hi,

It's kind of chain reaction polymerization which perhaps failed in initiation. In this this polymerization reaction TEMED and APS are the initiators and some environmental factor may helps the initiation like as light, temperature and oxygen content (reversely effects) of solutions. Using old acrylamide and bis might be helpful as in old solutions some degree of polymerization took place and this helps you to make firm gel with low initiator concentration, therefore changing to new solution was not a good idea as always. 

Hope it works this time. if not increase APS concentration to reach the optiamal concentration. 

Definitely use fresh APS.  That is your catalysis and helps make free radicals, so you want this fresh.  You can also try degassing your solution before the addition of the APS to remove air bubbles that might affect/quench the polymerization reaction.

Dear all,

why not trying a redox couple system such as K2S2O8/Na2S2O3 (Potassium persulfate/Sodium methabisulfate). A lot of benifits will be gained, especially the aformentioned system generates two initiating radicals from 1/1 molecules of the redox system, besides working at low temperature and high initiation efficiency. Regards

sory, the reducing agent structure is Na2S2O5. Regards

Thank you to both of you for your suggestions.

I will tried to use my old acrylamide and bis-acrylamide in addition to use the warm bath Idea. I have already tried to degas my solution before use, but I will try it again with the previous suggestions. I will let you know if it worked.

Did you remove the stabilizer from your monomers?

At which temp you carried out your reaction? I think you should increase temp.

Hi,

I finally managed to solve my PA gel polymerisation issue by reducing the concentration of ammonium persulfate to 0.5% and using older acrylamide and bis-acrylamide (1 year).

Thank you all for your suggestion,